This invention relates to exercise apparatus for use in a body of water which supports the weight of the user, and particularly, but not limited to, to therapeutic exercise apparatus wherein the effort required by the user is continuously and instantaneously variable for accommodating the instantaneous needs of each user.
It is generally known that the performance of various exercises while the exerciser's body is at least partially submerged in water makes it possible to exercise only desired muscles while avoiding undesired stresses on other portions of the exerciser's body. This is particularly important for persons who are exercising for therapeutic purposes, e.g., in the recovery from an accident or illness. In such instances, it is essential that the exercise be performable in a non-stressful manner, with only the desired muscles being exercised and at only a selected level of stress and effort.
Any number of exercise apparatus exist for exercising different muscles of the human body, see, for example, U.S. Pat. Nos. 4,529,194 and 4,659,077, the subject matter of which are incorporated herein by reference. However, when it is contemplated to use these known apparatus for therapeutic type exercising, and particularly for underwater use, various problems are presented.
A major one of such problems is that, in order to provide resistance to movement of various apparatus parts manipulated by the user, to provide the desired exercise, various weights, springs, levers and the like are used which generally provide, for a given setting, a fixed amount of resistance. In therapeutic exercising, however, where the exerciser can be in a quite weakened and easily tired condition, any level of fixed resistance can be undesirable as causing excessive tiring and stressing of the user. What is desired is a continuously variable resistance which is instantaneously responsive to the user's needs.
Another problem associated with the use of known exercise apparatus in an underwater environment is that water, and particularly chlorinated water, is corrosive, and the known apparatus, which employ pulleys, springs and the like to provide resistance to movement of the apparatus engaged members, are not well suited for use in such environment. The movable parts tend to quickly corrode, and providing proper lubrication of the movable parts is particularly troublesome. A need exists, therefore, for exercise apparatus of the aforementioned type which, however, is better suited for underwater use and which, preferably, is less complicated and easier to manufacture.